package com.etc.common.util;


/**
 * 
 * 
 * @author zhangliang
 * @version 1.0
 * @
 */

public class LatLonUtil {
	private static final double PI = 3.14159265; 
    private static final double EARTH_RADIUS = 6378137; 
    private static final double RAD = Math.PI / 180.0; 
 
    //@see http://snipperize.todayclose.com/snippet/php/SQL-Query-to-Find-All-Retailers-Within-a-Given-Radius-of-a-Latitude-and-Longitude--65095/  
    //The circumference of the earth is 24,901 miles. 
    //24,901/360 = 69.17 miles / degree   
    /** 
     * @param raidus 单位米 
     * return minLat,minLng,maxLat,maxLng 
     */ 
    public static double[] getAround(double lat,double lon,int raidus){ 
         
        Double latitude = lat; 
        Double longitude = lon; 
         
        Double degree = (24901*1609)/360.0; 
        double raidusMile = raidus; 
         
        Double dpmLat = 1/degree; 
        Double radiusLat = dpmLat*raidusMile; 
        Double minLat = latitude - radiusLat; 
        Double maxLat = latitude + radiusLat; 
         
        Double mpdLng = degree*Math.cos(latitude * (PI/180)); 
        Double dpmLng = 1 / mpdLng; 
        Double radiusLng = dpmLng*raidusMile; 
        Double minLng = longitude - radiusLng; 
        Double maxLng = longitude + radiusLng; 
        //System.out.println("["+minLat+","+minLng+","+maxLat+","+maxLng+"]"); 
        return new double[]{minLat,minLng,maxLat,maxLng}; 
    } 
     
    /** 
     * 根据两点间经纬度坐标（double值），计算两点间距离，单位为米 
     * @param lng1 
     * @param lat1 
     * @param lng2 
     * @param lat2 
     * @return 
     */ 
    public static double getDistance(double lng1, double lat1, double lng2, double lat2) 
    { 
       double radLat1 = lat1*RAD; 
       double radLat2 = lat2*RAD; 
       double a = radLat1 - radLat2; 
       double b = (lng1 - lng2)*RAD; 
       double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) + 
        Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2))); 
       s = s * EARTH_RADIUS; 
       s = Math.round(s * 10000) / 10000; 
       return s; 
    } 
}
